Excess smoke eliminating system for boilers

ABSTRACT

A SYSTEM TO DETECT EXCESS SMOKE IN THE SMOKE STACK OF AN OIL-FIRED INDUSTRIAL BOILER AND TO AUTOMATICALLY REDUCE THE OIL SUPPLY TO THE BURNER OF THE BOILER WHILE ALLOWING SAID BURNER TO CONTINUE TO OPERATE, THUS ELIMINATING EXCESS SMOKE WHICH WOULD OTHERWISE BE DISCHARGED THROUGH THE SMOKE STACK.

Oct. 31, 1972 v. DUCASSE 3,701,622

I EXCESS SMOKE ELIMINATING SYSTEM FOR BOILERS Filed Nov. 25, 1970 INVENTOR Viateur DU CASSE BY W AGENT United States Patent Int. Cl. Fzsn /08 US. Cl. 431-76 Claims ABSTRACT OF THE DISCLOSURE A system to detect excess smoke in the smoke stack of an oil-fired industrial boiler and to automatically reduce the oil supply to the burner of the boiler while allowing said burner to continue to operate, thus eliminating excess smoke which would otherwise be discharged through the smoke stack.

The present invention relates to industrial type boilers using heavy oil or bunker oil as fuel and normally attended to by a stationary engineer.

It is known that such boilers often produce black smoke which is no longer permitted by air pollution control agencies, particularly in cities. This black smoke or excess smoke is due to an uncontrolled increase in the rate of flow of the heavy oil supplied to the burner and caused by solid particles in the oil or other temporary phenomena. Because the upper end of the smoke stack is not normally visible to the stationary engineer, it is known to install a smoke detecting system on the smoke stack, which system is arranged to give an alarm in the boiler room, in order to warn the stationary engineer that the oil flow control valves must be adjusted in order to eliminate the excess smoke. However, it often happens that the stationary engineer is somewhere else than in the boiler room when the alarm is given and that, even if he hears or sees the alarm, a time interval of several minutes occurs between the time of the alarm and the time in which the oil control valves have been properly adjusted to eliminate the excess smoke.

Moreover, smoke detectors, of known type and which incorporate a photoelectric cell and electric light bulb mounted in aligned holes in the smoke stack of the boiler, become rapidly coated with soot and, consequent ly, give false alarms.

It is the general object of the present invention to provide a system to detect the presence of excess smoke in the smoke stack of an industrial boiler or the like and which automatically and immediately decreases the flow rate of oil to the burner of the boiler, in order to eliminate the formation of excess smoke While enabling the boiler to continue to operate and which also gives an alarm to notify the stationary engineer that it is necessary to readjust the oil flow valves, in order to restore the system into normal operating condition.

Another object of the present invention resides in the provision of a system of the character described, using a photoelectric cell and an electric light bulb to actuate the cell, mounted in the smoke stack in such a manner that the cell and light bulb will not become coated With soot and will not be affected by the heat of the gases flowing through the smoke stack.

Another object of the present invention resides in the provision of a system of the character described, which is highly sensitive, that is which operates immediately upon detection of a small excess of smoke relative to the normal smoke quantity, whereby, in practice, the system in accordance with the invention eliminates all smoke excess Within at the most one or two minutes following the start of the discharge of excess smoke from the upper end of the smoke stack.

Another object of the present invention resides in the provision of a system of the character described, which is of fail-proof and eflicient operation, which is of simple and inexpensive construction and which can be installed or mounted on any existing industrial boiler.

The foregoing and other objects of the present invention will become more apparent during the following disclosure and by referring to the drawings, in which:

FIG. 1 is a schematic elevational view of an industrial boiler and of the system for eliminating excess smoke in accordance with the invention;

FIG. 2 is a cross-section through the smoke duct taken along line 22 of FIG. 1;

FIG. 3 is a schematic electric and hydraulic circuit of the system in accordance with the invention; and

FIG. 4 is a schematic hydraulic circuit in accordance with a modification of the system of the invention.

In the drawings, like reference characters indicate like elements throughout.

Reference numeral 1 indicates an industrial boiler, partially shown in front end elevation, and provided with a smoke duct 2 for conveying the smoke or combustion gases to an exterior smoke stack or chimney, not shown.

The boiler 1 is provided with an oil burner 3 supplied with heavy oil or bunker C oil from a pipe 4 connected to the oil burner, the oil flowing through the pipe 4 in the direction of arrow 3. The pipe 4 is provided with a manual control valve 5 for adjusting the flow of the oil.

The oil is supplied under pressure by a pump normally controlled by a pressure responsive electric switch mounted on pipe 4. This electric switch or pressostat has a diaphragm exposed to the oil pressure at the end of a by-pass pipe in communication with pipe 4 and it often happens that this by-pass pipe becomes blocked by solid particles in the oil. The pump is no longer controlled by the pressostat and, therefore, the oil pressure within pipe 4 increases excessively and the amount of oil supplied to the burner increases and upsets the normal air and oil ratio to be supplied for proper oil combustion. Therefore, a black smoke issues from the smoke stack.

An abnormal increase in the oil rate of flow can be produced by other factors, for example when the oil is at an abnormally low temperature and, therefore, of too high a viscosity which might happen during, or immediately after, filling the oil tanks.

The system in accordance with the invention comprises a smoke detector and means controlled by this detector for automatically decreasing the amount of oil supplied to the burner and thereby eliminating the production of excess smoke. The detector itself comprises a photoelectric cell 6 and an electric light bulb 7 associated with smoke duct 2. More particularly, the photoelectric cell 6 and light bulb 7 are each mounted in a box or casing 8 and 9 respectively, secured on each side of smoke pipe 2. These casings 8 and 9 and the lateral walls of smoke pipe 2 are provided with openings 10 and 11 transversely aligned, whereby the light beam emitted by electric bulb 7 passes through smoke pipe 2 and illuminates the photoelectric cell 6.

Casings 8 and 9 are moreover provided with openings 13 and 14 respectively, made at the back of these casings and allowing ambient air to be sucked in by smoke pipe 2, While flowing through the casings '8 and 9 all around the photoelectric cell 6 and the light bulb 7, in order to cool these elements and maintain the same at ambient temperature despite the proximity of the hot gases flowing through smoke pipe 2 and also to prevent any soot particle from depositing on the electric light bulb and the photoelectric cell. These two elements are connected to electric wires, which are protected by tubes 15 and one of which enters a control box 16 mounted in the boiler room at a location accessible to the stationary engineer.

On the front panel of the control box 6 are mounted an electric switch 17 for the entire electric circuit of the system; a pilot lamp 1 8 to indicate that the system is operating; an electric alarm bell 19; the rotary knob of a rheostat 20 to control the amount of light emitted by electric light bulb 7 and an alarm light bulb 21.

Inside the control box 16, are mounted, as shown in FIG. 3, a transformer 22 for the circuit of the alarm bell 19; a solenoid valve 23, the valve body of which is series connected with a pipe 24 extending through the control box 16. The latteralso houses a connector block for the electric wires.

Pipe 24 is supplied with air, water or stream under pressure flowing in accordance with arrow 25 and its portion downstream from solenoid valve 23 is connected by a T 26 to a diaphragm valve 27 series connected with pipe 4 for the supply of heavy oil.

Diaphragm valve 27 is constructed to close pipe 4 when the diaphragm is subjected to fluid pressure supplied by pipe 24 when solenoid valve 23 is open. The other branch of T 26 is fitted with a plug 28 having a pin hole to permit slow discharge of the air or steam under pressure contained in the diaphragm chamber of valve 27 and in pipe 24 downstream from solenoid valve 23 when the latter is closed. Therefore, diaphragm valve 27 opens slowly when solenoid valve 23 is closed in order to slowly reestablish normal supply of heavy oil to the burner 3.

On the other hand, pipe 4 is provided with a by-pass 29 by-passing diaphragm valve 27. By-pass pipe 29 is provided with a manually-operated valve 30.

Referring to the electric circuit of FIG. 3,.the latter comprises wires 31 connected to a standard electric 110- volt alternating current supply. Wires 31 are series connected with electric switch '17 and supply electric light bulb 7, while one of the wires 31 is series connected with rheostat 20, in order to control the degree of lighting of light bulb 7. Pilot light 18 is parallel connected with light bulb 7. Wires 32, 33 are parallel connected with light bulb 7 and pilot light 18. Wire 32 is connected by a wire 34 to one terminal of the solenoid of solenoid valve 23' and to series-connected resistances 35 and 36 and, finally, to the stationary contact 37 of a relay, generally shown at 38. Wire33 is connected to the movable contact 39 of relay 38. Stationary contact 37 is also connected to other terminal of solenoid valve 23 by means of a wire 40.

The solenoid of relay 38 is connected to wire 33 and is series connected with photoelectric cell 6, the other terminal of which is connected to wire 34- between resistances 35 and 3 6.

A condenser 42 is parallel connected with the contacts of relay 38.

The photoelectric cell 6 is of the type the conductance of which increases with the increase in the incident light and is preferably a cadmium cell.

Solenoid valve 23 is parallel connected with alarm light 21 and the primary of transformer 22, the secondary of which is connected to the terminals of alarm bell 19. Solenoid valve 23 closes pipe 24 when not supplied with electricity and opens pipe 24 when energized. Diaphragm valve '27 normally opens pipe 4 when said valve is not subjected to air or steam or water pressure. The system of the invention operates in the following manner:

During normal operation of burner 3, the solenoid valve 23 is closed and, therefore, the diaphragm 'valve 27 is open and combustion oil flows normally in pipe 4 through diaphragm valve 27 and manual valve 5. Switch 17 is closed whereby pilot light 18 is lighted, indicating that detector light bulb 7 is lighted. Bulb 7 illuminates photoelectric cell 6 which actuates relay 38, whereby movable contact 39 is maintained in a position opening the circuit to solenoid valve 23. Therefore, the latter remains in closed position.

Rheostat is adjusted to decrease the intensity of the light emitted by bulb 7 down to a point where photoelectric cell 6 allows pasage of electricity to the solenoid of relay 38 in an amount just suffi'cient to maintain the relay 38 in open condition with the movable contact 39 attracted against the action of the return spring 43 attached to said movable contact 39'.

As soon as there is abnormal increase of the flow of the heavy oil and that excess smoke starts to form in smoke duct 2, the intensity of the light beam illuminating photoelectric cell 6 decreases below a certain minimum and photoelectric cell 6, then receives insufficient light to main- 7 tain relay 38 in open position. The latter closes movable contact 39, making contact with stationary contact 37, thereby closing the electric circuit to the solenoid valve 23. Simultaneously, the circuit of the alarm ball 19 and alarm light bulb 21 is closed, producing an acoustic and luminous alarm. The solenoid valve 23 opens and air, Water or steam under pressure flows through pipe 24 and actuates diaphragm valve 27 which closes oil supply pipe 4, thereby stopping the major part of the oil flow. However, a certain quantity of oil continues to supply burner 3 through by-pass pipe 29. The by-pass pipe 29 is adjusted by manual valve 30 in such a manner to supply a limited flow of combustion oil but sutlicient for the burner to continue to operate at a lower output, such that the oil supplied to the burner will never be in excess with respect to the air and, thus, there will never be produced excess smoke when the burner is supplied by by-pass pipe 29.

To re-establish the system to its normal operating condition, the stationary engineer corrects the malfunction which has caused operation of the system and slightly closes manual valve 5 of oil supply pipe 4. Then, be decreases the resistance of rheostat 20 in order to increase the luminous intensity of electric light bulb 7 in order to cause re-opening of relay 38. When the relay 38 is open, the stationary engineer increases again the resistance of rheostat 20 in order to decrease the light intensity of light bulb 7 down to a value just suflicient for the photoelectric cell 6 to be conductive enough, for just enough current to pass through the relay 38 to maintain the same in open condition. Once the system is reset, the stationary engineer re-adjusts valve 5, if necessary.

It should be noted that relay 38 requires its full rated current to open, that is to attract movable contact 39 against the action of return spring 43 when the contact is away from the core of the core 41. However, once the movable contact abuts said core and, therefore, once the relay is in open position, it requires very little current to maintain the relay in open position. Thus, once the relay is open, increase of the resistance of the rheostat places the detecting system in a state of great sensitivity to detect the least amount of excessive smoke in the duct 2.

Resetting of the system to normal operating condition requires a manual operation from the part of the stationary engineer, that is handling of rheostat 20. This avoids automatic reset of the system which would happen once there is no more excess smoke in the smoke duct 2 and which would produce an uninterrupted succession of alarms and of opening and closing of diaphragm valve 27 until correction of the malfunction by the system had been corrected.

If electric bulb 7 burns out, the operator will be made aware thereof, because the alarm will again operate after partial closing of the manual valve 5 by the stationary engineer. In this case, he will know that said light bulb 7 is burnt out. However, a pilot light can be series con nected with electric bulb 7 to indicate that the latter is functioning.

When the stationary engineer produces re-opening of relay 38, solenoid valve 23' closes and, therefore, diaphragm valve 27 slowly opens, because the fluid under pressure in pipe 24 between valve 23 and valve 27 can discharge only slowly through the small pin hole made in the plug 28. Therefore, normal operation of the burner will be re-established in a smooth manner.

The electric circuit of the photoelectric cell 6 is standard: it comprises the cell 6, relay 38, resistances 35 and 36 and condenser 42. A preferred such unit is sold under the name Photoelectric Control, International Series K1321, by International Register Company, of Chicago, Illinois.

The system in accordance with the invention gives a long service without maintenance due, particularly, to the fact that the light bulb 7 and photoelectric cell 6 are mounted in casings 9 and 8 provided with openings 11 and 10 and 14 and 13 for air circulation through said casings and around the light bulb and photoelectric cell. Thus, the light bulb and cell are maintained at ambient temperature despite their proximity to the hot gases contained in duct 2 and, moreover, are hardly ever coated with soot, because the lower gas pressure within the smoke duct 2 causes fresh air circulation through casings 8 and 9. In certain cases, solenoid valve 23- can be directly mounted on oil supply pipe 4. In this manner, valve 27 and piping 24, 26 and 28 are dispensed with.

FIG. 4 illustrates another embodiment of the system in accordance with the invention, wherein the fuel oil is constantly recirculated through the fuel tank in order to prevent cooling of the fuel oil before it reaches the burner. The fuel tank 44 is connected to the burner 45 of the boiler by means of a pipe 46 provided with a fuel pump 47 and a manual valve 48, the latter corresponding to valve of the first embodiment.

A return pipe 49 is connected to tank 44 and to pipe 46 between pump 47 and manual valve 48. A diaphragm valve 27', which corresponds to the diaphragm valve 27 of the first embodiment, but which is normally closed instead of being normally open, is mounted in series in the return pipe 49, together with a first pressure regulating valve 50. A by-pass pipe 51, provided with a second pressure-responsive valve 52, is connected to return pipe 49 upstream of automatic diaphragm valve 27' and downstream from the first pressure regulated valve 50. The first pressure regulated valve 50 is set to open at a pressure less than the pressure required to open the second pressure regulated valve 52; for example at 65 pounds per square inch when the second relief valve 52 is set to open at about 75 pounds per square inch. The diaphragm valve 27' is caused to open by the same system which serves to close valve 27 of the first embodiment, that is by the smoke detector circuit, alarm system and solenoid valve 23, which are shown in FIG. 3.

The second embodiment operates in the following manner:

The fuel pump 47 supplies oil at a higher rate than that required by burner 45, whereby the surplus fuel oil returns to the tank 44 through the second pressure regulated valve 52, which is set at the higher opening pressure, it being understood that diaphragm valve 27' is normally closed. When there is detection of excess smoke within the smoke duct 2 by means of the photoelectric cell circuit 6, the automatic diaphragm valve 27' opens, whereby there is an increase of the rate of flow of oil returning to the tank, because of the lower pressure required to open the first pressure regulating valve 50. Therefore, the rate of flow of oil supplied to the burner 45 decreases and the excess smoke is eliminated. However, the burner continues to operate. The operation and resetting of the system is otherwise as in the first embodiment.

What is claimed is:

1. A system to detect excess smoke in the smoke duct of a boiler and to automatically eliminate said excess smoke, said boiler being provided with a fuel burner, a fuel tank and piping connecting the burner to the tank,

said system comprising a luminous source to produce a light beam through said smoke duct, a photoelectric cell actuated by said luminous beam from said luminous source, an automatic valve mounted on a portion of said piping and actuated by said photoelectric cell when said cell receives less light due to the presence of excess smoke in said smoke duct and a by-pass pipe connected to said piping portion on each side of said automatic valve and allowing supply of said burner, even when said automatic valve is actuated but at a lesser flow rate of fuel adjusted to prevent formation of excess smoke and wherein said photoelectric cell and said luminous source are located in casings secured to said smoke duct on each side of the latter, said smoke duct being in communication with said casings by openings allowing passage of air as well as the luminous beam, said casings being provided with additional openings communicating with the ambient air to allow passage of the ambient air through the casings and into said smoke duct, air circulation thus produced flowing around said luminous source and said photoelectric cell to maintain the same substantially at ambient temperature and substantially soot free.

2. A system as claimed in claim 1, wherein said photoelectric cell is of the type wherein the conductance increases with increase of the incident light, said photoelectric cell being connected in a circuit comprising a relay and a solenoid valve controlled by said relay and further including a rheostat series connected with said luminous source to vary the light intensity of the latter.

3. A system as claimed in claim 2, further including a second pipe supplied with fluid under pressure and connected to said automatic valve, the latter being a diaphragm valve, said solenoid valve being series connected with said second pipe and opening said second pipe only when supplied by electric current from said relay, said diaphragm valve being actuated when said solenoid valve is open. Y

4. A system as claimed in claim 3, wherein the portion of said second pipe between the diaphragm of said diaphragm valve and said solenoid valve is provided with a pin hole to allow slow discharge of fluid under pressure within said portion of said second pipe when said solenoid valve is closed.

5. A system to detect excess smoke in the smoke duct of a boiler and to automatically eliminate said excess smoke, said boiler being provided with a fuel burner, a fuel tank and piping connecting the burner to the tank, said system comprising a luminous source to produce a light beam through said smoke duct, a photoelectric cell actuated by said luminous beam from said luminous source, an automatic valve mounted on a portion of said piping and actuated by said photoelectric cell when said cell receives less light due to the presence of excess smoke in said smoke duct and a by-pass pipe connected to said piping portion on each side of said automatic valve and allowing supply of said burner, even when said automatic valve is actuated but at a lesser flow rate of fuel adjusted to prevent formation of excess smoke, and wherein said piping portion contains fuel circulating towards said burner and wherein said automatic valve is normally open.

6. A system as claimed in claim 5, wherein said by-pass pipe is provided with a manual valve to adjust the rate of flow of fuel circulating through said by-pass pipe.

7. A system to detect excess smoke in the smoke duct of a boiler and to automatically eliminate said excess smoke, said boiler being provided with a fuel burner, a fuel tank and piping connecting the burner to the tank, said system comprising a luminous source to produce a light beam through said smoke duct, a photoelectric cell actuated by said luminous beam from said luminous source, an automatic valve mounted on a portion of said piping and actuated by said photoelectric cell when said cell receives less light due to the presence of excess smoke in said smoke duct and a by-pass pipe connected to said piping portion on each side of said automatic valve and allowing supply of said burner, even when said automatic valve is actuated but at a lesser flow rate of fuel adjusted to prevent formation of excess smoke, and wherein said piping portion contains fuel circulating towards said reservoir and wherein said automatic valve is normally closed.

8. A system to detect excess smoke in the smoke duct of a boiler and to automatically eliminate said excess smoke, said boiler being provided with a fuel burner, 21 fuel tank and piping connecting the burner to the tank, said system comprising a luminous source to produce a light beam through said smoke duct, a photoelectric cell actuated by said luminous beam from said luminous source, an automatic valve mounted on a portion of said piping and actuated by said photoelectric cell when said cell receives less light due to the presence of excess smoke in said smoke duct and a by-pass pipe connected to said piping portion on each side of said automatic valve and allowing supply of said burner, even when said automatic valve is actuated but at a lesser flow rate of fuel adjusted to prevent formation of excess smoke, and wherein said piping comprises a first part connected between said reservoir and said burner, 21. fuel pump mounted in said first part, and a second part for the return of fuel connected to said tank and to said first part between said pump and said burner, said piping portion being constituted by said second part.

9. A system as claimed in claim 7, further including a first pressure regulated valve series connected with said automatic valve and a second pressure regulated valve connected to said by-pass pipe.

10. A system as claimed in claim 6, wherein said first pressure regulated valve is set to open at a smaller pressure than said second presusre regulated valve and wherein said automatic valve is normally closed.

References Cited UNITED STATES PATENTS 3,216,661 11/ 19 65 Sawyer 43l76 X 2,562,507 7/1951 Pierce 431-76 X 3,529, 5'84- 9/1970 Celaya 43113 X EDWARD G. FAVORS, Primary Examiner US. Cl. X.R. 236-45 E 

